My 2008 Volvo S60 has a fuel leak on the "sender" unit. I have replaced the black "screw" and the oring multiple times and it still leaks. It is better than it originally was, but still leaks. The last time, I tried using Permatex 85420 added to the oring, but it still leaked. Thinking about cutting a cork gasket instead. Also, when I tighten up the "screw", I can't keep the sender unit in the correct orientation even if I try to prevent the sender from twisting as I tighten the screw. I lubricated the bottom of the screw to minimize the friction with the sending unit as I tightened down the screw. I didn't mark the unit before I removed it so I don't know how tight is correct, but it is pretty tight. I have a tool which grabs onto the screw to help with loosening and tightening.

Does anyone have any suggestions? My son has a long commute. After I "fix" it and fill it up and discover it still leaks, I have to get him drive it on his commute to get the fuel down to a level that I can work on it again.

 

I took a closer look and the unit is not leaking from the Oring, but on the raised part on sender unit itself. I have a question. That raised part has no wires coming from it on my unit, but some units, like the one in the picture that I found on Youtube have a wire coming from it. In this picture, my unit has the wires with the red arrow, but not the wires with the green arrows. Does anyone know why there is a difference? Thanks in advance.